Expert: Rob Painter - 12/4/2010

Question
MY 1993 CADILLAC SEVILLE HAS BEEN RUNNING STRANGE IDLES
IRREGUGULAR AT TIMES ENGINE MISSES AND I GET THE ERROR CODES
PO85 AND PO32. TRIED TO RESET PCM BUT IT WONT RESET AND THE
CHECK ENGINE LIGHT STAYS ON HOW DO I CHECK THE PCM TO MAKE
SURE IT IS DEFECTIVE  

Answer
Hello,

I can only assist you partially here. It has been too long since I worked on the old GM computer system. In 1994 GM came out with a standardized computer system known as the OBD II, a year later than your car.

Now, don't go running out and getting a different computer because this may not fix your problem.

You have what is known as a hard code meaning that the problem needs to be fixed as soon as possible to maintain emissions.

A soft code can be erased and the engine won't start running bad until the check engine light comes on. Once it goes out, the engine will run good again.

All your engine running problems are related to your codes.

Your engine will not run properly until the computer system can go into closed loop. Closed loop is when all sensors and the computer are in sync with each other and the engine runs at optimum performance.

The problem with the codes is that you need to know what each one stands for and that will only tell you which circuit if you will is the problem.

For example: say you have a code 13 which is a soft code. This would be in the O2 sensor circuit, This could be a bad O2 sensor or a problem with the wiring. In this case, the check engine light would come on momentarily while driving. The engine would run rough only when the O2 sensor circuit was acting up. The code with stay in the computer until it is erased, but the check engine light only comes on at times.

You have a problem that requires immediate attention in order for the engine to run properly. It could be an ecm problem and maybe not.

I don't know if it will help, but you might be able to do a google search for 1993 Cadillac code PO2 and that may help.

You are going to need before you change anything to know what those codes mean in order to fix the problem.

I no longer have books this old. The library might have a 1993 Cadillac manual or you might go on ebay and search.

If the manual is over $30, don't waste the money and go to http://www.alldata.com Become a member and download all the factory repair manuals for the car. Membership is about $30 per year which gives you complete access to everything you need to diagnose any mechanical problem on your car.

This is where I go for vehicles I need the factory info on a specific car.

Good luck!

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